The provision of a clutch for an A.C. motor is somewhat of a "Catch 22" in that provision of an A.C. clutch requires collector rings to supply the current to the clutch parts. That is expensive and requires maintenance. The alternative is to use a D.C. clutch which requires a rectified voltage supply which entails an expense. This approach does, however, afford adjustment of the clutch torque or power transmission by changing the applied voltage. To adjust an A.C. clutch has required disassembly of the clutch to adjust the spring force or to change the springs. Both approaches represent compromises and costly compromises at that.